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Abstract
Market penetration of electric vehicles (EVs) is largely hindered by the lack of a nationwide fast charging network and limited drive range. The fast charging electric vehicle supply equipment (EVSE) is costly to implement on a large-scale due to the need for high power charging hardware comprising of multiple power electronic stages dedicated to delivering controlled power to the EV battery.
This thesis proposes an integrated charge and drive system for EVs. The concept is to utilize the on-vehicle powertrain as the EVSE, thus offering a cost-effective solution by eliminating the DC/DC power conversion stage from the EVSE. The integrated system consists of two energy sources paired with drive inverters that are connected in series through an electric motor with a simple open-stator winding, where the charging input is accessed from the differential connection of the inverters. In comparison to previous fast charging integrated solutions that require the use of two power stages in the traction system to enable integrated charging, the proposed integrated solution only requires a single power stage in the traction drive. While the dual energy sources integrating hybrid energy storage media may consist of two identical battery packs, the powertrain can be further leveraged to potentially extend drive range.
Charging and driving features of the integrated system are verified in simulation and experiment, through development of a 110kW motor drive test bench integrating dual energy sources of both similar and differing characteristics. The experimental results demonstrate feasibility of utilizing traction hardware to regulate the charging current under established constant-current and constant-voltage battery charging modes. A balancing control strategy is also developed to equalize the energy between the dual energy sources. For vehicle propulsion, the results demonstrate flexible power sharing between two energy sources under static & dynamic driving conditions, where in the case of a battery and supercapacitor, power & energy management of the supercapacitor is achieved without reliance on a two-stage power electronic solution. Numerical efficiency comparison between existing traction drives and the proposed traction drive shows up to 14% additional range from an electric vehicle using the proposed system in an urban setting.
